And of course, this is Heath Ledger's last-ever film.

Thousands of years ago Dr Parnassus (a great romp for The Sound of Music's Christopher Plummer) won immortality in a bet with the devilish Mr Nick (Tom Waits). But Dr Parnassus traded his immortality for youth when he met the love of his life, on the condition that Mr Nick, the Devil, could collect their child's soul on its 16th birthday.

Dr Parnassus also has a drinking habit to fund and other debts to pay, and his magic powers are used in a sideshow act, bringing imaginations to life inside the "Imaginarium".

Dr Parnassus' Imaginarium is a rickety old horse-drawn sideshow which creaks through the streets of modern London. While it promises to unlock dreams and imagination, no-one seems to notice it. Only drunks and computer-game obsessed children seem to wander in.

With his daughter, Valentina (Lily Cole), the adoring Anton (Andrew Garfield) and Percy (Verne Troyer, Mini-Me from Austin Powers in Goldmember), Dr Parnassus and his Imaginarium struggle on, until they save the enigmatic Tony from death.

Enter Heath Ledger. His silver-tongued charms transform their show, bringing rewards as jaded shoppers step through the Imaginarium's magic mirror, coming out seconds later swinging with joy and emptying their purses. Literally. But Tony's dubious past catches up with him around about the same time as the Devil, Mr Nick, comes to collect Parnassus' daughter.

The Devil offers Parnassus a final way out, and it merely requires him to collect more souls that the Devil in the Imaginarium.

It's when we step through the mirror that the screen lights up with Gilliam's brilliant imagery and vivid colours, in stark contrast to the dark gothic streets of London. You can feel his joy as he teases us without visual boundaries, and each scene is a hallucinogenic trip. The only problem is you may not want to return to the story.

Heath Ledger was apparently still buzzing from his performance as The Joker in Dark Knight and adlibs a lot of his role. It's a performance which shows off his versatility rather than his quality. A range of A-list actors (Johnny Depp, Jude law and Colin Farrell) fill in the missing scenes when Tony steps through the mirror, so we forgive the crazy changes and accept it as a tribute of sorts. There was so much more to come.

There are some great performances, particularly by Plummer, Troyer and Waits. Garfield (Lions for Lambs) is more annoying than endearing, and Lily Cole (St Trinian's) is a better supermodel than actress. And Heath's Dark Knight role had more power.

Parnassus' story — one which Gilliam jokingly referred to as autobiographical — is of the struggling artist who wants people to lose themselves in their imagination for a time through the magic of the artist. It is also about making deals with the Devil and others' dreams of an ordinary existence.

The sprawling story loses its focus at times, probably because Gilliam was lost in the Imaginarium himself, which is understandable. If you're in the mood for a fun ride, with some black humour and bright visuals, strap yourself in. It's a wild place to be.

Your say: Have you seen this film? What did you think? Did you enjoy Heath's performance?